Known are waterless lithographic printing plates having an ink-repellent layer of silicone rubber or fluorine resin, for which various types of photosensitive plates have heretofore been proposed to be processed through selective exposure and development.
Waterless lithography is a type of lithographic printing method requiring no water for wetting printing plates in operation, in which, in the printing plate to be used, the image area of an ink-receiving layer and the non-image area of an ink-repellent layer are basically in nearly the same flat surface of the plate. In such waterless lithography, ink is adhered only to the image area of the printing plate owing to the difference in the ink affinity between those two layers, and the thus-adhered ink is then transferred onto printing substances such as paper. The non-image area is of an ink-repellent material such as fluorine resin, and no water is used in printing.
For example, for non-processed plates for waterless, positive lithographic printing plates, proposed were those comprising a photo-polymerizable photosensitive layer and an ink-repellent layer of silicone rubber as laminated on a support, for example, in JP-B Sho-54-26923 and Sho-56-23150; and those comprising a photo-dimerizable photosensitive layer and an ink-repellent layer of silicone rubber as laminated on a support, for example, in JP-B Hei-3-56622 and JP-A Sho-61-153655. For non-processed plates for waterless, negative lithographic printing plates, proposed were those comprising a photo-peelable photosensitive layer of a polyfunctional isocyanate-crosslinked, partial ester of phenol-formaldehyde novolak resin with 1,2-naphthoquinone-2-diazido-5-sulfonic acid chloride, and an ink-repellent layer of silicone rubber as laminated on a support in that order, for example, in JP-B Sho-61-54222.
Those non-processed plates are generally exposed to active rays through positive or negative film, and then developed, whereby only the ink-repellent layer corresponding to the image area is removed and the photosensitive layer and, as the case may be, the underlying primer layer or support are exposed out to be the ink-receiving image area.
For non-processed photosensitive plates for waterless lithographic printing plates having an ink-repellent layer of fluorine resin, disclosed are those having an ink-repellent layer of fluorine resin with 1H,1H,2H,2H-heptadecafluorodecyl methacrylate, for example, in JP-A Hei-2-254449 and Hei-2-85855.
Various photo-reactive compounds have heretofore been proposed to be usable in the photosensitive layers for non-processed plates for waterless, positive lithographic printing plates of the known ones noted hereinabove. For example, JP-B Sho-54-26923 and JP-A Hei-5-281717 disclose methods of using specific amino group-having monomers for producing non-processed plates for high-sensitivity waterless lithographic printing plates, but the disclosed methods are problematic in that the non-processed plates produced therein are often adversely affected by the basic amino groups and their image reproducibility is worsened while they are stored for a long period of time.
JP-A Hei-1-237663 and Hei-2-237663 disclose methods of using polymers having ethylenic unsaturated groups in their side chains, which, however, are problematic in that the non-processed plates produced therein do not have good image reproducibility since the polymerization efficiency of the ethylenic unsaturated groups in the polymers used is much lower as compared with that in monomers, and that the adhesiveness between the photosensitive layer and the overlying ink-repellent layer in the plates is poor. In order to solve these problems, they proposed a combination of amino-free, hydroxyl-having monomers and the polymers, which, however, was ineffective owing to the difference in the reaction speed between the ethylenic unsaturated groups in the side chains of the polymers and the monomers, but rather interfered with the polymerization reaction of the monomers with the polymers to worsen the image reproducibility of the plates. In addition, the proposed combination was ineffective in improving the image reproducibility of the plates as both the polymers and the monomers participate in the adhesion between the photosensitive layer and the overlying ink-repellent layer, and could not still improve the adhesiveness of the ink-repellent layer to the photosensitive layer.
Moreover, the conventional, waterless lithographic printing plates are problematic in that the photosensitive layers therein have, after having been exposed, too high initial elasticity, and are therefore broken at their adhesion interface in long-term printing, especially offset printing operation. In particular, in industrial-scale, waterless, rotary lithographic offset printing operation where repeated stress is imparted to the printing plate during ink transfer between the printing plate and the blanket, the conventional printing plates are often broken at the adhesion interface between the photosensitive layer and the ink-repellent layer and their printing durability is poor.
The present invention is to solve these drawbacks in the prior art, and its object is to provide non-processed plates for waterless lithographic printing plates with good storage stability, which are processed into waterless lithographic printing plates having good printing durability and which are characterized in that a photopolymerizable compound having a specific structure is incorporated into the photosensitive layer to improve the adhesiveness between the photosensitive layer and the overlying ink-repellent layer and that between the photosensitive layer and the underlying support or primer layer and to improve the polymerization efficiency of the photosensitive layer.